The permanent alteration of the colour of keratinous fibres, in particular human hair, by the application of hair dyes is well known. In order to provide the consumer with the hair colour and the intensity of colour desired, a very complex chemical process is utilized. Permanent hair dyeing formulations typically comprise oxidative hair dye precursors, which can diffuse into the hair through the cuticle and into the cortex where they can then react with each other and suitable oxidising agents to form the end dye molecules. Due to the larger size of these resultant molecules they are unable to readily diffuse out of the hair during subsequent washing with water and/or detergents; hence delivering a consumer-desired permanency of colour. This reaction typically takes place in an aggressive environment at approximately pH 10 in the presence of an alkalizing agent and in the presence of an oxidizing agent. Moreover, the consumer repeats this process regularly in order to maintain the desired hair colour and shade and the intensity of colour and to ensure continual, even coverage of the hair including coverage of new hair growth.
The manufacturer of such products is also required to work within a large number of constraints. Since these products are being placed in direct contact with the consumers' skin, the potential exists for accidental contact with the eye or for ingestion (for example), which can occur during the dyeing process. Therefore, the formulation must meet rigorous safety requirements and not induce any allergic reactions. In addition to meeting these requirements, the products must also be optically and olfactory pleasing to the consumer. In particular, the products also need to meet certain physical parameters in order to ensure that the product can be easily applied to the hair by the consumer to provide the desired effect, without unintentional staining of the consumers' clothes, skin or other objects.
The manufacturer is also required to provide the hair colouring consumer a large range of different resulting colours. Some consumers may just wish to enhance the natural colour of the hair, whilst others may wish to cover grey or completely alter the hair colour to a different natural appearing hair colour or a ‘synthetic’ appearing hair colour. Consequently, the manufacturer may provide over twenty different formulations, of varying colours and shades, to address the range of consumer specific needs. These formulations have to be individually formulated and are typically complex formulae containing a mixture of different dye compounds. As a result the manufacture of such product ranges can be costly and complex.
However, despite the fact that commercial hair dyeing products have been available for many years, the products still exhibit a number of consumer-related deficiencies.
Typically permanent hair dye products will contain an alkali, typically a source of ammonia. This serves the purpose of swelling the hair allowing the entry of the dye precursor molecules into the hair and also improves the lightening effect of the oxidising agent, which is typically hydrogen peroxide. However, ammonia is also volatile and its associated odour is extremely unpleasant to the consumers' of such products, particularly as these hair dye products are used in close proximity to the nasal region. Hence, it would be highly desirable to provide an oxidative hair colouring and/or bleaching composition, which delivers the consumer required lightening level and colour but which has reduced or eliminated the detectable ammonia odour.
In fact another deficiency area in current hair colouring products is the provision of hair colouring products which deliver the required hair lightening effect. Delivering the required level of lightening is particularly important in order to provide the full range of colour shades demanded by the consumer, especially for blonde shades and grey coverage. Such products pose particular difficulties to the manufacturer, as they usually require the use of high levels of oxidising agent and ammonia in order to deliver the required lightening effect. However, in additional to the problems associated with the presence of high levels of ammonia in these products, as discussed herein above, the presence of these high levels of ammonia and/or oxidizing agent also affect the condition of the hair and may in some cases induce mild skin irritation on the scalp. In particular, the hydrophilicity of the hair surface is increased during the colouring process, which alters the sensory perception of the hair and its overall manageability during, immediately after colouring and during the subsequent wash and styling cycles until the next colourant application. Hence, it would also be highly desirable to provide an oxidative hair colouring and/or bleaching composition which delivers the required lightening and/or colour without unnecessary hair damage.
A number of attempts have been described in the literature to address at least some of the above identified improvement areas. For example the use of carbonate has been described in the following hair colouring art.
EP 435 012 describes hair-dyeing compositions, which require a short dyeing time, create little damage to hair, and no irritating odour after dyeing comprising a carbonate source, a non odour generating alkali hydrogen peroxide and a buffer solution. Similarly EP 1 106 166 describes hair dye compositions comprising ammonia, carbonate (other than ammonia salt), transition metal salt and chelating agent which do not give off an irritating odour, have low skin irritation and can change the hair colour into a lighter tone in a short time. WO01/28508 describes hair colouring formulations comprising oxidising agents and ammonia carbonate or carbamate which deliver improved bleaching and colouring with reduced odour and hair damage without the need for buffering agents, pH modifiers or hair swelling agents. JP01206825 describes a low pungent hair colouring composition comprising ammonia, ammonium salt and carbonate. The composition may also comprise alkanolamine to improve resistance to decolouration.
JP11343219 discloses hair bleaching compositions comprising ammonia, or ammonium ion and carbonate ion. Similarly DE 296 13 065 U1 discloses a hair beaching powder comprising hydrogen peroxide, ammonium salt and alkali carbonate or alkali hydrogen carbonate.
However it has now been found that a problem related to the use of hydrogen peroxide and carbonate hair colourant systems is that, particularly in the presence of high levels of peroxide and carbonate, the hair colourant compositions can under certain conditions result in significant damage to the hair fibres. Consequently, the hair fibres are substantially weakened and may become so brittle that breakage occurs during the consumers' normal hair maintenance routine.
Another particularly critical performance area for the consumer is the provision of the desired resultant colour and also the effective coverage of grey hair. Indeed, whilst the amount of grey hair to be coloured varies considerably from consumer to consumer, the resultant overall appearance of the coloured hair demanded by the consumer should be nearly identical for the naturally pigmented hair and the grey hair on head, with the added requirement that the initial coverage is maintained during the post dyeing washing and drying cycle.
Hence, it would be further desirable to provide the consumer with a hair colourant, providing improved lift and lightening, reduced damage, particularly brittle fibre formation, and improved colour delivery, uptake and durability.
It has now been surprisingly found that oxidative hair colouring compositions comprising an oxidising agent, a source of carbonate ions, an alkalising agent, preferably a source of ammonia and a specific radical scavenger as defined herein below utilised at a pH 9.5 and below provide a low odour colouring composition which delivers a high level of lift and lightening equal to the currently utilised ammonia/peroxide systems, whilst reducing the concentration of peroxide and reducing the hair fibre damage. Moreover, the compositions of the present invention are compatible with current dyes and dye precursor systems and result in improved lift and lightening for blond shades, excellent dye deposition and colour and improved grey coverage.
A number of documents in the literature describe a large number of a wide variety of compounds, which may be considered to have radical scavenging activity for use in beauty care products. For example EP840593A describes an oxidative hair colourant comprising developers and optionally couplers, having a pH of 8 to 11 and an alkalising agent comprising a mixture of amino acids and oligopeptides and certain alkanolamine derivatives to reduce ammonia odour and reduce hair damage. U.S. Pat. No. 3,899,288 describes keratinous fibre oxidative dyeing compositions comprising oxidative dye precursors, and a carbonate alkali metal salt of an amino acid for reducing ammonia odour. Similarly, DE2215303 discloses hair dyeing compositions comprising guanidine compounds, arginine protamine or polypepetides oxidative dye precursors and peroxide, to provide odour free compositions and which do not cause skin irritation. U.S. Pat. No. 3,997,659 describes hair bleaching compositions containing arginine or various proteins or peptides having a high arginine content, peroxide and a bleaching accelerator to reduce odour and reduce hair damage.
However, none of these documents describe the features and benefits of the presently claimed invention.